The ATR-72, a twin-engine turboprop aircraft used for short distances, went down about 50 minutes into the 350-mile journey, said a spokesman for the airline, Mohammad Taghi Tabatabaei.

Officials earlier said 66 people were aboard the plane, but the state-run IRNA news agency reported later that one person listed as a passenger had missed the flight. There were 59 passengers and six crew members on the flight, the news agency said.

The cause of the crash was not immediately known, although airline officials blamed bad weather in the mountains. Rescue workers said they were having difficulty landing air ambulances near the crash site due to heavy fog.

State-run Iranian media reported that the same aircraft — one of six in the airline’s fleet — suffered from technical problems during a flight out of Tehran 23 days ago, forcing the pilot to return to Mehrabad.

The Iranian Students News Agency reported that the captain of that flight, Hojjatollah Foladi, was flying the plane that crashed Sunday.

Aseman Airlines, a semi-private carrier and one of the country’s largest, flies mainly to domestic destinations but also operates international flights to Istanbul, Dubai and Kuwait City.

Hobbled for decades by sanctions and trade restrictions, Iran’s domestic airline industry maintains one of the world’s oldest passenger fleets.

Poor condition of aircraft is often cited as a reason Iran suffers from one of the world’s worst air safety records. Since 1979, about 1,700 people have died in more than 90 aircraft-related accidents, according to the Flight Safety Foundation.

Since the lifting of most international sanctions in 2016 following the agreement Iran struck with world powers to curb its nuclear program, the U.S. manufacturer Boeing and its European rival, Airbus, have each agreed to sell Iran scores of passenger planes.

The Trump administration has threatened to block the transactions, arguing the aircraft could be used by the Iranian military.